1. Field of the Invention
The present invention relates to a portable terminal. More particularly, the present invention relates to an apparatus for controlling the operation of a portable terminal including a plurality of display units.
2. Description of the Related Art
In general, the term “portable terminal” refers to a communication apparatus that a user can carry to wirelessly communicate with another user. Such portable terminals are extensively used among individuals. Also, such terminals are recently being provided with the ability to perform various kinds of useful functions in accordance with the Digital Convergence era. For example, with such a portable terminal, the user may perform Audio On Demand (AOD) and Video On Demand (VOD) services, may have visual communication with another user, or may download games to play. Also of interest is the user's ability to obtain high quality content (e.g. high quality moving pictures or online games) through a High-Speed Downlink Packet Access (HSDPA) service. With these newer functions and capabilities, it is desirable that the size of a display unit of a portable terminal be made larger. However, a portable terminal is limited in size due to its portability. One option for maintaining the terminal's overall size while increasing the size of the display is to develop the portable terminal toward excluding the key input unit therefrom (e.g. an i-phone produced by Apple company) or minimizing the number of keys in the key input unit thereof. However, such a portable terminal causes a wide variety of inconveniences for the user to input characters thereto. In order to address such inconveniences, the user may be provided with a portable terminal including two displays (dual display). The dual display portable terminal is a two-sided portable terminal including first and second surfaces thereof. The first surface has a display unit of a large size which is suitable for the multimedia environment and a minimized key input unit. The second surface has a display unit of a small size, which is suitable for normal communication, and a plurality of keys. Although there is an advantage in that such dual-display portable terminal can be more conveniently used in the multimedia environment, the dual-display portable terminal consumes more power, thereby shortening the usable time of the portable terminal. Therefore, in order to improve the continuous use of the portable terminal, a removable case having a battery mounted therein is required. The removable case has an advantage in increasing the usable time of the portable terminal. On the other hand, the removable case has a disadvantage in that it is difficult to achieve screen-shift between two display units. Particularly, the removable case has a structure to cover an exterior of each display unit so as to protect each display unit of the dual-display portable terminal. Therefore, a significant effort is required to open/close the removable case whenever the user uses the portable terminal. Even if the removable case is absent, the user has to achieve screen-shift between two display units, depending on the user's necessity, by using a screen shift key. Therefore, with respect to portable terminals having a plurality of display units, there is a need for providing a portable terminal which can easily achieve screen shift without a separate key input.